Primary CNS Lymphoma

KEY FACTS

TERMINOLOGY

• Malignant primary CNS neoplasm primarily composed of B

lymphocytes (PCNSL)

IMAGING

• Best diagnostic clue: Enhancing lesion(s) within basal

ganglia &/or periventricular white matter

• 60-80% supratentorial

○ Often involve, cross corpus callosum

○ Frequently contact, extend along ependymal surfaces

• Classically hyperdense on CT (helpful for diagnosis)

• Diffusely enhancing periventricular mass in

immunocompetent patients

• May see hemorrhage or necrosis in immunocompromised

patients

• DWI: Low ADC values

• PWI: Low relative cerebral blood volume ratios

• Periventricular location and subependymal involvement is

characteristic of PCNSL

• Corpus callosum involvement may be seen with PCNSL,

glioblastoma (GBM), and rarely metastases or

demyelination

TOP DIFFERENTIAL DIAGNOSES

• Acquired toxoplasmosis

• GBM

• Abscess

• Progressive multifocal leukoencephalopathy

PATHOLOGY

• 98% diffuse large B-cell, non-Hodgkin lymphoma

CLINICAL ISSUES

• Imaging and prognosis vary with immune status

• 6.6% of primary brain tumors, incidence rising

• Poor prognosis

• Stereotactic biopsy, followed by chemotherapy, ± XRT

(Left) Axial graphic shows

multiple periventricular

lesions with involvement of

the basal ganglia, thalamus,

and corpus callosum, typical of

primary CNS lymphoma

(PCNSL). Note the extensive

subependymal spread of the

disease ﬈. PCNSL typically

extends along ependymal

surfaces. (Right) Axial T1 C+

MR in a 63 year old shows the

classic appearance of PCNSL.

Note the multiple

homogeneously enhancing

masses in the basal ganglia

along the ependymal lining of

the ventricular system ﬈.

(Left) Axial T1 C+ MR shows a

homogeneously enhancing

mass crossing the corpus

callosum splenium ﬊ typical

of PCNSL in this 76-year-old

man with a headache. The

main differential

consideration would be a

glioblastoma, which typically

has a more heterogeneous

appearance. (Right) Axial

T1WI C+ MR in an AIDS patient

shows a ring-enhancing mass

with a target sign ﬈,

suggestive of toxoplasmosis.

Hemorrhage, necrosis, and

ring-enhancing lesions are

typical of PCNSL in AIDS

patients.

Cysts, and Disorders

Brain: Pathology-Based Diagnoses: Neoplasms,

147